The present invention relates to a linear pulse motor and more particularly to a guide mechanism for a movable member of a linear pulse motor which may be used as motors for feeding heads of floppy disc drive, electronic printers, etc.
Representative guide mechanisms for a movable member of a linear pulse motor were proposed in U.S. patent application Ser. No. 711,153 entitled "SUPPORTING MECHANISM FOR A MOVABLE MEMBER OF LINEAR PULSE MOTORS" and filed on Mar. 13, 1985, of which disclosure is incorporated herein by reference. FIG. 1 illustrates one of the guide mechanisms, in which a movable member 1 has a teeth portion 1a, as a secondary unit, formed in its lower face and a stator 2 as a primary unit includes a pair of cores 5 and 6 wound with coils 3 and 4, each core having comb-shaped magnetic poles 5a, 5b or 6a, 6b formed in upper faces of respective ends of its legs. The lower faces of the end portions of the legs of each core 5 or 6 are bonded to a permanent magnet 7. Each core 5 or 6 is provided on the upper faces of its legs with an angular guide member 8 or 9 to be directed to corresponding magnetic poles 5a, 5b or 6a, 6b to define a travel path. Further, each of cores 5 and 6 has a supporting member 21 placed on its travel path between the corresponding guide member 8 or 9 and magnetic poles 5a, 5b or 6a, 6b. As clearly shown in FIG. 2, each supporting member 21 has a pair of rollers 18 and 18, rotatably fitted in retaining holes 21b formed through a horizontal flange 21a thereof, and a pair of balls 20 and 20 rotatably fitted in respective retaining recesses 23 and 23 formed in its vertical flange 21c. Each supporting member 21 is in rolling contact by it rollers 18 with the upper face of the core 5 or 6 at its travel path so that it may travel along the travel path, and is stopped at opposite ends of the travel path by stoppers 19 mounted there.
When the movable member 1 is placed on the cores 5 and 6 so that the teeth portion 1a is placed above the magnetic poles 5a, 5b, 6a and 6b, the movable member 1 is brought at opposite lateral peripheries 1b and 1b of its lower face into contact with rollers 18 and 18 of the supporting members 21 and 21 and at its opposite lateral edges 1c and 1c into contact with balls 20 and 20, with the result that the teeth portion 1a and the magnetic poles 5a, 5b, 6a and 6b are opposed with a small gap. The movable member 1 is stepwisely moved on the stator 2 by supplying electric pulses to coils 3 and 4.
The linear pulse motor above described is excellent in reduction in size, particularly thickness, and in cost, but its movable member 1 is liable to reduce its stroke during a long term operation. That is, although theoretically the displacement of the supporting members 21 and 21 is a half of the displacement of the movable member when the linear pulse motor is energized, the displacement of the former in practice becomes considerably smaller than a half of that of the latter during its long term operation due to disturbances caused by roughness of the travel path faces, dusts adhered to them, scratches produced in them, etc. Thus, the movable member 1 cannot move in the worst case.